Tuesday, July 28, 2009

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A quick check of the NOAA NOMADS system for the OI.v2 SST data revealed that the preliminary July 2009 data had been posted yesterday. Based on the schedule listed in the following FAQ page, the data will not be finalized until July 10.http://www.emc.ncep.noaa.gov/research/cmb/sst_analysis/FAQ.html

So here’s a brief early look at the direction the global and NINO3.4 SST anomaly data are headed. Preliminary July 2009 Global SST anomaly data is showing a very slight drop, -0.02 deg C, since June 2009, while NINO3.4 SST anomalies are continuing their rise. Preliminary July 2009 NINO3.4 SST anomalies are 0.93 deg C, up 0.32 deg C since June. The graphs follow.

And comparing the July and June maps in an animated gif, the unusual warm area in the Northeastern tropical Pacific appears to be ebbing as the waters along the equator are warming. Is this a result of the increased convection over the equator as SST there rises? This would cause an inflow of winds and, in turn, probably lower the SST in the adjacent tropics as the surface waters are drawn toward the equator.http://i28.tinypic.com/2rzbdph.gif
Comparison of June and Preliminary July 2009 Global SST Anomaly Maps
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Preliminary July 2009 Global SST Anomalies
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Preliminary July 2009 NINO3.4 SST Anomalies

This post illustrates why regression analyses do not capture the multiyear aftereffects of significant El Nino events. To emphasize this, I’ve provided a detailed explanation of the processes that take place before, during, and after those significant El Nino events, using graphics and videos from earlier posts.

EXAMPLE OF RESULTS FROM A REGRESSION ANALYSIS

Regression analyses are used by climatologists to determine and illustrate the impact on global temperature of one or more variables, such as ENSO, Solar Irradiance, and Volcanic Aerosols. Figure 1 shows the results of one such study. It is a multi-cell illustration of “Surface Temperature Variability Components” from Lean and Rind (2008) “How Natural and Anthropogenic Influences Alter Global and Regional Surface Temperatures: 1889 to 2006” [GEOPHYSICAL RESEARCH LETTERS, VOL. 35, L18701, doi:10.1029/2008GL034864, 2008].
Link to Paper:http://pubs.giss.nasa.gov/docs/2008/2008_Lean_Rind.pdfhttp://i32.tinypic.com/2lmw477.png
Figure 1

My Figure 1 is Figure 2 from Lean and Rind (2008). Under the heading of “Datasets”, Lean and Rind write, “Monthly fluctuations in ENSO, volcanic aerosols, solar irradiance and anthropogenic influences are shown in Figure 2. The multivariate ENSO index, a weighted average of the main ENSO features contained in sea-level pressure, surface wind, surface sea and air temperature, and cloudiness [Wolter and Timlin, 1998], extends from 1950 to 2006. It is augmented with an index derived from Japan Meteorologial Agency sea surface temperatures from 1868 [Meyers et al., 1999]. Volcanic aerosols in the stratosphere are compiled by [Sato et al., 1993] since 1850, updated from giss.nasa.gov to 1999 and extended to the present with zero values. The adopted solar forcing, consistent with IPCC [2007], is less than half that reported in prior IPCC assessments. Monthly irradiances since 1882 are estimate d from competing effects of sunspots and faculae in observations made by space-based radiometers, extended into the past using solar flux transport simulations [Wang et al., 2005]. The anthropogenic forcing is the net effect of eight different components, including greenhouse gases, landuse and snow albedo changes, and (admittedly uncertain) tropospheric aerosols [Hansen et al., 2007] (inset, Figure 2d).”

Lean and Rind then go on to detail the analyses they performed. Under the heading of “Amplitudes and Patterns of Natural and Anthropogenic Influences,” they state, “Natural changes cannot account for the significant long-term warming in the historical global surface temperature anomalies. Linear trends in temperature attributed to ENSO, volcanic aerosols and solar irradiance over the past 118 years (depicted by the lines in Figure 2) are, respectively, 0.002, -0.001 and 0.007 K per decade. Only by associating the surface warming with anthropogenic forcing is it possible to reconstruct the observed temperature anomalies.”

Basically, using a short-term comparison of NINO3.4 SST anomalies and Global RSS MSU TLT anomalies, my Figure 2, regression analyses like those used by Lean and Rind argue that natural variables cannot explain the upward divergence of global temperature from NINO3.4 SST anomalies. And if natural variables cannot explain the additional rise in global temperature, then the anthropogenic global warming hypothesis dictates that anthropogenic forcings must cause the rest. BUT…http://i32.tinypic.com/2rw9pbq.png
Figure 2

REGRESSION ANALYSES TREAT ENSO AS A “FORCING”, NOT AS A PROCESS WITH MULTIYEAR AFTEREFFECTS

Regression analyses regard El Nino events as a climate forcing of varying frequency and magnitude, the same way they consider other natural forcings such as volcanic aerosols and solar irradiance. They do not consider the multiyear processes that can occur after those El Nino events. Before presenting these, I’ll first provide a detailed description of the processes that take place before, during, and after significant El Nino events.

During non-El Nino years (La Nina and ENSO-neutral years), warm water accumulates in an area of the western tropical Pacific known as the Pacific Warm Pool (PWP); also known as the Indo-Pacific Warm Pool (IPWP). Refer to Figure 3.http://i30.tinypic.com/b3tpah.gif
Figure 3 (Source CRCES. Link to follow.)

Some of the warm water in the Pacific Warm Pool is water that returns there after El Nino events (the Equatorial Countercurrent in the Pacific relaxes after an El Nino and the North and South Equatorial Currents move the warm water back from the eastern to the western equatorial Pacific). More on that later. Some of the warm water in the Pacific Warm Pool results from solar radiation that warms the tropical Pacific and from the trade winds that push those warm surface waters from east to west in the Pacific during La Nina events and during ENSO-neutral periods. And some of the buildup of warm water in the Pacific Warm Pool occurs during the El Nino event itself, when cloud amounts over the Pacific Warm Pool drop significantly, causing a major rise in downwelling shortwave radiation (visible light). During the 1997/98 El Nino, it has been estimated that downwelling shortwave radiation rose as much as 25 watts/sq meter over the PWP. Refer to Figure 4. (This change in downwelling shortwave radiation was discussed in my post Recharging The Pacific Warm Pool Part 2.)

The accumulation of warm water in the Pacific Warm Pool over months and years from trade winds pushing surface waters west, the periodic transport of the warm water out of the PWP by El Nino events, the blast of downwelling shortwave radiation during El Nino events, and the replenishment of the warm water during the subsequent La Nina all cause the size and temperature of the Pacific Warm Pool to vary.

Note how, during the 1997/98 El Nino, the Western Equatorial Pacific Warm Water Volume (light blue curve) drops as NINO3.4 SST anomalies (black curve) rise. This is one indication that the warm water is being carried away from the Pacific Warm Pool during the El Nino event. Also note how quickly the Western Equatorial Pacific Warm Water Volume replenishes itself. It has “recharged” by the second phase of the 1998/99/00 La Nina.

The direction shifts in the Pacific Equatorial Currents that are part of an El Nino show how the warm water volume of the Pacific Warm Pool is lowered during those events. The Equatorial Countercurrent increases in size and carries the warm water from the Pacific Warm Pool to the east. When the El Nino ends, the Equatorial Countercurrent ebbs, and the North and South Equatorial Currents carry the warm water back to the west, to the Pacific Warm Pool. These shifts can be seen in Video 1 “Equatorial Currents Before, During, and After The 1997/98 El Nino” from my post of the same name:http://bobtisdale.blogspot.com/2009/02/equatorial-currents-before-during-and.html

And there are subsurface changes that take place during an El Nino event. The warm water that was in the Pacific Warm Pool, most of it below the surface, shifts east during the El Nino, where it rises to the surface. These changes in the subsurface waters of the Pacific can be seen in my Video 2 “Cross-Sectional Views of Three Significant El Nino Events – Part 1”. Link to post:http://bobtisdale.blogspot.com/2009/02/cross-sectional-views-of-three.html

Though not discussed in Video 2, the rise of the thermocline at the end of the 1997/98 El Nino is visible. “Rewind” to minute 3:00 and start the video. After the commentary, the thermocline rises, further illustrating that warm water that was once below the surface of the Pacific Ocean has been brought to the surface by the El Nino.

Some BUT NOT ALL of the warm water that had sloshed east during the El Nino returns to the Pacific Warm Pool during the subsequent La Nina. And the warm water that doesn’t return to the Pacific Warm Pool is carried westward by the Equatorial Currents of the Pacific, Figure 7, to the surface of the Western Pacific and the Eastern Indian Oceans.http://i30.tinypic.com/wvzu6r.png
Figure 7

In other words, warm water that was below the surface of the Pacific Warm Pool (and not included in the calculation of global temperature anomaly) is redistributed around the surface of the nearby oceans by the El Nino, (and it is now included in the calculation of global temperature). Phrased yet another way, before that El Nino, the warm water was not included in surface temperature record but afterward the warm water was included in surface temperature record. This raises global temperature anomalies without any heat input. Keep in mind that the rearranging of waters during an El Nino does not in and of itself create heat; it only shifts warm water from below the surface of the Pacific Ocean to the surface where it impacts temperature measurements.

THIS CAN BE SEEN AS UPWARD STEP CHANGES IN THE SEA SURFACE TEMPERATURE OF ~25% OF THE GLOBAL OCEANS

And those upward step changes after the 1986/87/88 and 1997/98 El Nino events can be seen in the sea surface temperatures of the East Indian and West Pacific Ocean, the black curve in Figure 9. Also illustrated in Figure 9 are scaled NINO3.4 SST anomalies (purple curve) and Sato Index data (green curve), which I’ve added to illustrate the timing of explosive volcanic eruptions that impact sea surface temperature (and global temperature).http://i31.tinypic.com/24l5rlw.png
Figure 9

The area represented by the East Indian and West Pacific Ocean SST anomalies (the black curve in Figure 9) is shown in Figure 10.http://i39.tinypic.com/5n55as.jpg
Figure 10

SEA SURFACES OUTSIDE OF THE EQUATORIAL PACIFIC ARE ALSO WARMED BY THE EL NINO THROUGH THE EXCHANGE OF HEAT FROM THE ATMOSPHERE TO THE OCEAN

During the El Nino events, heat from the surplus of warm surface waters along the equatorial Pacific is pumped into the atmosphere where it is carried around the globe. This raises land surface temperatures, (not illustrated). And the higher atmospheric temperature also raises the surface temperature of the oceans outside of the tropical Pacific. These increases in SST can be seen in Video 4 “Global SST Anomaly Animation 1996 to 2009”. Video 4 is from my post “Animations of Weekly SST Anomaly Maps from January 3, 1996 to July 1, 2009.” There is no narrative with Video 4. The description is included in the post.

The exchange of heat from atmosphere to ocean in the East Indian and West Pacific Oceans adds to the elevated surface temperatures that are caused by the warm water that had been carried there by ocean currents, discussed earlier. The El Nino also warms the East Pacific, South Atlantic, and West Indian Oceans through the atmosphere. Those portions of ocean basins are in turn cooled by the La Nina event that follows. But there is another portion of an ocean basin where the heat from the El Nino lingers; that is, the SSTs of that ocean basin are not impacted proportionately by the La Nina. And that ocean basin is the North Atlantic.

THE SST ANOMALIES OF THE NORTH ATLANTIC ALSO HAVE UPWARD STEP CHANGES AFTER SIGNIFICANT EL NINO EVENTS

The title of the linked post “There Are Also El Nino-Induced Step Changes In The North Atlantic” explains the content. And these SST anomaly step changes in the North Atlantic correlate well with the step changes in the East Indian and West Pacific Oceans, though they result from different aftereffects of the significant El Nino events. Refer to Figure 11. Keep in mind that the North Atlantic is also impacted by the Atlantic Multidecadal Oscillation.

Assuming the North Atlantic represents approximately 15% of the global ocean surface area, then the East Indian and West Pacific plus the North Atlantic account for approximately 40% of the global ocean surface area. In the years that follow significant El Nino events, ocean currents and atmosphere-ocean processes “mix” the lingering elevated SST anomalies of the East Indian, West Pacific and North Atlantic Oceans with the remaining 60% of the global oceans. This causes the rise in global SST anomalies that presents itself as the divergence of Global SST anomalies from NINO3.4 SST anomalies, similar to that shown in Figure 2. That natural increase in SST anomalies is mistaken for warming due to anthropogenic causes.

The RSS MSU Time-Latitude Plots of Global TLT illustrate the transport of heat from the tropics toward the poles that result from significant El Nino events. This is illustrated and discussed in detail in my post “RSS MSU TLT Time-Latitude Plots...Show Climate Responses That Cannot Be Easily Illustrated With Time-Series Graphs Alone”. In that post, I combined Time-Series Graphs with the Time-Latitude Plots to show the effects of the significant El Nino events. But even without the time-series graphs, the 1997/98 El Nino is easy to find in Figure 12. It appears as an area of elevated tropical TLT anomalies that begins in 1998 and ends about a year later. Note that most of the heat that had been in the tropics is transported to the mid-to-high latitudes of the Northern Hemisphere, where it lingers through the 1998/99/00 La Nina. Regression analyses cannot capture that lingering aftereffect of an El Nino.http://i42.tinypic.com/2hfukjm.jpg
Figure 12

The Time-Latitude Plots also show the impacts of the 1986/87/88 El Nino and limited TLT response to the 1982/83 El Nino. Refer to Figure 13. The 1982/83 El Nino was counteracted by the explosive eruption of El Chichon.http://i41.tinypic.com/2vwzmdj.jpg
Figure 13

THE DIFFERENCE BETWEEN SIGNIFICANT EL NINO EVENTS AND THE OTHERS

This post primarily discussed the processes and aftereffects of the significant El Nino events of 1986/87/88 and 1997/98, using the 1997/98 El Nino as reference in many of the discussions and links. There were two other significant El Nino events since 1970, the 1972/73 and 1982/83 El Nino events. The 1982/83 El Nino was counteracted by the eruption of El Chichon, which turned it into a nonentity. As illustrated in Figure 14, there are striking similarities between the multiyear periods that followed the 1972/73, 1986/87/88, and the 1997/98 El Nino. This was discussed in detail in my post “Similarities of the Multiyear Periods Following Significant El Nino Events Since 1970.” Are these lesser El Nino events simply aftereffects of the significant El Ninos?

Regression analyses do not account for the multiyear aftereffects of significant El Nino events and do not account for the resulting El Nino-induced step changes in SST, TLT, and Land Surface Temperatures. Regression analyses falsely attribute the divergence of global temperature anomalies from NINO3.4 SST anomalies to anthropogenic causes when, in fact, the divergence is caused by the lingering aftereffects of significant El Nino events. The additional rise in global temperatures after the significant El Nino events is in reality caused by subsurface waters from the Pacific Warm Pool being transported to the surface and remaining there after the El Nino event has ended.

SOURCES

Sources of the data used in the graphs are provided in the linked posts.

Wednesday, July 22, 2009

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As noted in prior Sea Level posts (Sea Level Update - Through March 2009 and Sea Level Data: Global and Indian, Atlantic, and Pacific Oceans), the sea level data available from the University of Colorado is not in monthly format. Some years there may be 38 readings, for example, while for others there may be 35. And to complicate matters, the total number of readings for the global dataset is different than the individual ocean subsets. For this post, I converted the Global Sea Level data and the Sea Level data for the Atlantic, Indian, and Pacific Oceans into monthly data.

I apportioned the data by sampling dates. For example, if the dates of the readings were greater than or equal to “1983.000” but less than “1983.083”, the data was considered January 1983 data and all readings for that month were averaged. And I repeated the process each month from December 1982 to March 2009.

In this post I have also provided comparisons to scaled NINO3.4 SST anomalies. As could be expected, some of the rises and falls are related to ENSO events. The step changes also appear to be direct responses to El Nino events. I am not, however, implying that Sea Level variability is only impacted by ENSO.

GLOBAL SEA LEVEL

The monthly Global Sea Level data from December 1992 to March 2009 is illustrated in Figure 1. The late 1995 spike in the sea level data stands out similarly to the way the 1997/98 El Nino stands out in global temperature data.http://i31.tinypic.com/op5nw1.png
Figure 1

Figure 2 compares Global Sea Level to scaled NINO3.4 SST anomalies. The peak in late 2005 is not directly related to an El Nino. The impacts of the 1997/98 and the 2002/03 El Nino events, however, can be seen in the Global Sea Level data.http://i31.tinypic.com/2mrgo5x.png
Figure 2

MONTHLY SEA LEVEL FOR THE ATLANTIC, INDIAN, AND PACIFIC OCEANS

As preliminary notes, the annual variability in the Atlantic and Indian Ocean Sea Level data can be clearly seen in the monthly data. The Pacific data is noisier, which masks an annual signal.

Note how the smoothed Atlantic Sea Level data, Figure 3, appears to rise in steps. The first step is in 1995. This should be a rebound from the Mount Pinatubo aerosol effects.http://i27.tinypic.com/zs4m0.png
Figure 3

The scaled NINO3.4 SST anomaly data has been added in Figure 4. The smoothed Atlantic Sea Level data rises again in 1997, which should be a response to the 1997/98 El Nino. Are the rises in 2003 and 2005 also responses to the 2003/04 and 2004/05 El Nino events?http://i32.tinypic.com/t8nrch.png
Figure 4

The raw and smoothed Indian Ocean Sea Level data, Figure 5, show a major step change in 1998 and a curious increase in trend in 2004.http://i31.tinypic.com/25qzrdi.png
Figure 5

The 1998 upward step in the smoothed Indian Ocean Sea Level data appears to be a lagged response to the 1997/98 El Nino. Refer to Figure 6. The 2004 change in trend does not appear to be ENSO related. Was there a shift in Indian Ocean cloud cover in 2004?http://i31.tinypic.com/1415glt.png
Figure 6

Following the significant increase from 1998 to 2002, the Pacific Ocean Sea Level, Figure 7, has been relatively flat since 2002. The rise in Pacific Sea Level slowed after 2002, and Pacific Sea Level has declined since 2006.http://i31.tinypic.com/hsta3q.png
Figure 7

In the comparison with NINO3.4 SST anomalies, Figure 8, note how the Pacific Ocean Sea Level surged upward in mid-1996, one year before the 1997/98 El Nino. Does this indicate that there was a sudden rise in ocean heat content in the year leading up to that El Nino? Does this confirm the findings in my post “Did A Decrease In Total Cloud Amount Fuel The 1997/98 El Nino?” It does seem to show that the 1997/98 El Nino was fueled by a short-term change (one year) in the ocean heat content of the Pacific.http://i28.tinypic.com/2enn4lk.png
Figure 8

ATLANTIC, INDIAN, AND PACIFIC OCEAN COMPARISONS

Figure 9 is a comparison of Sea Levels for the Atlantic, Indian, and Pacific Oceans. Note how one dataset always appears to be out of phase with the variations of the other two. Rarely do the sea levels of all three oceans rise or fall in unison.http://i30.tinypic.com/2wh2k9f.png
Figure 9

The SST anomalies for the Atlantic, Indian, and Pacific Oceans are illustrated in Figure 10. There are significant differences between the SST and Sea Level curves. (I can’t see any reason to compare the individual ocean sea level and SST data.)http://i32.tinypic.com/2gxl5ja.png
Figure 10

It is likely that NINO3.4 SST anomalies will increase over the next four to five months. It is unlikely (but not impossible) for the Global SST anomalies to continue their decline while NINO3.4 SST Anomalies are rising.

Sunday, July 19, 2009

This post presents graphs of raw, smoothed, and annualized sea level data for Global, Indian Ocean, Atlantic Ocean, and Pacific Ocean data sets. The recently updated data is available through the University of Colorado at Boulder. Here’s a link to their Sea Level Change Overview (index) webpage:http://sealevel.colorado.edu/index.php
and a link to their Time Series Data Page:http://sealevel.colorado.edu/results.php

Note 1: You’ll note the graphs of the raw and smoothed data include the notation “Smoothed w/ 35-Period Filter”. The number of samplings varies per year, from 35 one year to 38 the next for example. Keep that in mind when viewing the data. To assure that the smoothing did not misrepresent the data, I’ve also presented the annual mean of the data sets in separate graphs from 1993 to 2008.

Note 2: All of the data sets include the seasonal signals and they exclude the inverted-barometer adjustments.

GLOBAL SEA LEVEL

Figure 1 shows the Global Sea Level for the period of December 1992 to March 2009. Global Sea Level appears to have risen at a reasonably constant rate until mid-2005, when the rate of rise decreased.http://i27.tinypic.com/2q8dfyc.png
Figure 1

Looking at the annual data from 1993 to 2008, Figure 2, confirms the sharp deceleration in the rise of Global Sea Level in 2006 through 2008.http://i31.tinypic.com/vn369k.png
Figure 2

INDIAN OCEAN

The Indian Ocean Sea Level data is shown in Figure 3. Based on the smoothed data, the Indian Ocean Sea Level remained flat from early 2007 to early 2008, then rose again since then. Also note the multiple swings in sea level during 1996 and 1997, leading up to the El Nino of 1997/98.http://i28.tinypic.com/24q0qw6.png
Figure 3

Figure 4 illustrates the annual Indian Ocean Sea Level from 1993 to 2008. The rate at which Indian Ocean Sea Level was rising (appears to have been increasing exponentially) finally slowed in 2008.http://i29.tinypic.com/4rvw9y.png
Figure 4

ATLANTIC OCEAN

The raw sea level data for the Atlantic Ocean is illustrated in Figure 5. Based on the smoothed data , the Atlantic Ocean Sea Level does not appear to have risen since 2005.http://i30.tinypic.com/dy6bo0.jpg
Figure 5

The annual Atlantic Ocean Sea Level data confirms this. Refer to Figure 6. Atlantic Ocean Sea Levels remained flat in 2006, dropped in 2007, then rose slightly in 2008, but 2008 levels are still lower than those in 2005 and 2006.http://i32.tinypic.com/xkt56a.png
Figure 6

Saturday, July 18, 2009

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Figure 1 shows the Global SST anomalies for June 2009. The pattern in the Pacific is unusual, at least for the months of May, June, and July from 1982 to 2008, as will be shown. While preparing my recent post “Animations of Weekly SST Anomaly Maps from January 3, 1996 to July 1, 2009” and the future posts that animate SST anomalies back through 1982, I’ve downloaded more than 1,000 SST anomaly maps of the Pacific. I can’t recall that pattern in any of them regardless of the month. Note how most of the Tropical Pacific (bordered in green) has positive SST anomalies. There are a few areas with neutral or slightly negative anomalies, but for the most part the anomalies are positive. That by itself is unusual. And the pattern in the Mid-to-High Latitudes of the North Pacific is also unusual. I’ve never seen it before. It may have occurred before 1982, it may have occurred during prolonged negative PDO periods decades ago, but I do not remember seeing it in any of the maps since 1982.http://i28.tinypic.com/20z8fo0.png
Figure 1

To illustrate this, I prepared a video that compares the June 2009 Global SST anomaly map to the June maps from 1982 to 2008, alternating between them and June 2009 as the video progresses--similar to a long-term blink comparator. Since 1982, the same pattern occurred in no other June. I also repeated the process for the May and July maps, comparing them to June 2009, and again the same pattern has not occurred. Has it been present during other months since 1982? I don’t know for sure. Has it occurred at any time before 1982? I don’t know. I have documented is that it has not occurred during the months of May, June, or July from 1982 to 2008. And I believe that extending the comparisons beyond those months would be fruitless.

The first possible explanation that comes to mind for the unusual SST anomaly pattern in the Pacific is a shift in cloud cover, but I have not been able to find either a cloud cover or cloud amount dataset that is updated through June 2009.

The “Contour interval for var1” was set at 0.2 deg C to bring out the lower-intensity temperature anomalies. “white” was set at “0” so that blues represented negative anomalies and reds represented positive anomalies. All four videos last for approximately 2 1/2 minutes.

Please click on the videos to watch them in a larger size at YouTube. There they can be expanded to full screen and set to high definition.

In addition to the surges of heat in the North and South Atlantic during El Nino events, there are a number of paths that warm SST anomalies enter the South Atlantic during ENSO neutral and La Nina periods. Occasionally, the Benguela Current carries these warm water anomalies north along the Southwest Coast of Africa, where they are then carried west by the Atlantic Equatorial Currents. The warm anomalies either return to the South Atlantic, following the currents of the South Atlantic gyre, or they enter the North Atlantic. Once in the North Atlantic, they travel north, and appear to do that quickly. These additions of elevated SST anomalies during La Nina and ENSO-neutral periods also help explain why There Are Also El Nino-Induced Step Changes In The North Atlantic.

The Indian Ocean animation shows very “noisy” SST anomalies, without any obvious reoccurring pattern. I was hoping to illustrate evidence of the Indian Ocean Dipole. In a future post, I’ll try to do so.

ENSO events stand out in the Pacific Ocean SST anomaly animation. It is possible to differentiate between traditional El Nino events like the 1997/98 El Nino (initially forms in the eastern equatorial Pacific) and the El Nino Modoki events of 2002/03 and 2004/05 (initially form in the central equatorial Pacific). Occasionally, the Pacific Decadal Oscillation (PDO) pattern in the North Pacific (north of 20N) makes its presence known, as does the basin-wide pattern of the Interdecadal Pacific Oscillation (IPO).

In a future post, I’ll discuss a sequence of events that appears to occur during traditional El Nino events. Note how, before the formation of the 1997/98 El Nino, the Humboldt Current carries warm Southern Hemisphere SST anomalies up along the west coast of South America to the eastern equatorial Pacific. Yet RSS MSU TLT Time-Latitude Plots (refer to RSS MSU TLT Time-Latitude Plots...) clearly show that the majority of the heat from the 1997/98 El Nino was transported to the mid-to-high latitudes of the Northern Hemisphere. Does this mean that El Nino events transport heat from the Southern Hemisphere to the Northern Hemisphere?

In addition to the processes that appear in the videos of the three major oceans and the interactions between them, the Global SST anomaly animation also shows the seasonal shifts in the SST anomalies within the Northern and Southern Hemispheres. There also appears to be a shift between them, where the higher SST anomalies appear during the summer months for each hemisphere.

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The 1982/83 and 1997/98 El Nino events are considered the significant ENSO events of the 20th century. Their peak SST anomalies stand above all others. Refer to Figure 1. Well…maybe not. As Karl reminded in the El Nino – same but different thread at WattsUpWithThat, the 1972/73 El Nino came in a close third.

Figure 2 is a 150-month-long comparison of NINO3.4 SST anomalies for the 1972/73 and 1997/98 El Nino events and for the decades or so following them. With the exception of the upswing at the end of the 1972/73 El Nino (purple) curve and the downswing at the end of the 1997/98 El Nino (brown) curve (the upswing and downswing are the 1982/83 El Nino and the 2007/08 La Nina, respectively), the two curves of the secondary upsurges in NINO3.4 SST anomalies are remarkably similar.http://i25.tinypic.com/166y9vt.png
Figure 2

The explosive eruption of El Chichon in 1982 minimized (eliminated?) the heat transport from the 1982/83 El Nino event. This can be seen in an MSU TLT Time-Latitude Plot from RSS, Figure 3. So for this post, we’ll consider the 1982/83 El Nino to be dysfunctional and exclude it from this post.http://i25.tinypic.com/dopbgj.jpg
Figure 3

And soon after the effects of the volcanic aerosols from El Chichon subsided, the 1986/87/88 El Nino occurred. Referring back to Figure 1, the SST anomalies of the 1986/87/88 El Nino did not peak as high as the 1972/73 and 1997/98 El Nino events, but the 1986/87/88 El Nino lasted through the entire year of 1987. The end result, there was a noticeable redistribution of heat from the 1986/87/88 El Nino, Figure 4. So in that respect, the 1986/87/88 El Nino was also a significant El Nino.http://i27.tinypic.com/2upwivn.jpg
Figure 4

In Figure 5, I’ve added the NINO3.4 SST anomalies of the 1986/87/88 El Nino to the 150-month-long comparison with the 1972/73 and 1997/98 El Nino events. The 1986/87/88 El Nino also created a multi-year secondary surge in NINO3.4 SST anomalies that was similar in scale to the other two events.http://i27.tinypic.com/2gt6k5t.png
Figure 5

Smoothing the three curves with 25-month running-average filters, Figure 6, helps illustrate the similarities in the three curves.http://i29.tinypic.com/sc6fz6.png
Figure 6

CLOSING QUESTION

From 1970 to present (and excluding the 1982/82 El Nino), are the lesser El Nino events that occurred after the significant El Nino events of 1972/73, 1986/87/88, and 1997/98 simply aftereffects?

Wednesday, July 8, 2009

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I’ve prepared this post for those who want to compare El Nino Modoki Index data to NINO3.4 SST anomalies. I did not standardize the El Nino Modoki Index data. Note also that I scaled the NINO3.4 SST anomaly data by a factor of 0.5 to bring it into line with the El Nino Modoki Index data.

Last, keep in mind that the El Nino Modoki Index is a calculated value. Ashok et al describe the calculation as follows:

“EMI= [SSTA]A-0.5*[SSTA]B-0.5*[SSTA]C (1)

“The square bracket in Equation (1) represents the area-averaged SSTA over each of the
regions A (165E-140W, 10S-10N), B (110W-70W, 15S-5N), and C (125E-145E, 10S-20N), respectively.”

Figure 1 illustrates those regions used in the El Nino Modoki Index. Keep in mind that the declines in the SST anomalies in Regions B and C help raise the El Nino Modoki Index, and vice versa.http://i31.tinypic.com/33xeziu.png
Figure 1

Figure 2 is a long-term comparison of El Nino Modoki Index data and NINO3.4 SST anomalies. In Figures 3 through 6, I’ve shortened the time spans. I have not attempted to provide the threshold for the El Nino Modoki events on the graphs. You’ll have to scale that value on your own. You can use Figures 2 and 3 and the accompanying dialogue in my post There Is Nothing New About The El Nino Modoki for reference, but remember that the threshold was established for the standardized data.

Comment Policy, SST Posts, and Notes

Comments that are political in nature or that have nothing to do with the post will be deleted.####The Smith and Reynolds SST Posts DOES NOT LIST ALL SST POSTS. I stopped using ERSST.v2 data for SST when NOAA deleted it from NOMADS early in 2009.

Please use the search feature in the upper left-hand corner of the page for posts on specific subjects.####NOTE: I’ve discovered that some of the links to older posts provide blank pages. While it’s possible to access that post by scrolling through the history, that’s time consuming. There’s a quick fix for the problem, so if you run into an absent post, please advise me. Thanks.####If you use the graphs, please cite or link to the address of the blog post or this website.